Nitrile rubber (NBR)-clay nanocomposites were prepared by co-coagulating the NBR latex and clay aqueous suspension. Transmission electron microscopy showed that the silicate layers of clay were dispersed in the NBR matrix at the nano level and had a planar orientation. X-ray diffraction indicated that there were some nonexfoliated silicate layers in the NBR-clay nanocomposites. Stress-strain curves showed that the silicate layers generated evident reinforcement, modulus, and tensile strength of the NBR-clay nanocomposites, which were significantly improved with an increase in the amount of clay, and strain-at-break was higher than that of the gum NBR vulcanizate when the amount of clay was more than 5 phr. The NBR-clay nanocomposites exhibited an excellent gas barrier property; the reduction in gas permeability in the NBR-clay nanocomposites can be described by Nielsen's model. Compared with gum NBR vulcanizate, the oxygen index of the NBR-clay nanocomposites increased slightly. The feasibility of controlling rubber flammability via the nanocomposite approach needs to be evaluated further. (C) 2003 Wiley Periodicals, Inc.